About us
About Sleep Time Calculator
Why this site exists
Most sleep advice tells you to "get 8 hours" — but anyone who has woken up groggy after a full eight hours knows the number alone is not the answer. Timing matters: waking from lighter sleep at the end of a cycle often feels easier than being pulled out of deep sleep.4 Sleep Time Calculator exists to make that timing easier to plan. The 90-minute figure is an adult average, not a personal measurement.1
What we built
The site is a small, focused set of free tools: a sleep time calculator that works out your ideal bedtime or wake-up time from 90-minute cycles, a nap length guide, a sleep debt calculator with a realistic repayment plan, a jet lag recovery planner, and a written guide to how sleep cycles work. Every tool runs entirely in your browser — no sign-up, no downloads, nothing sent to a server.
How we write our content
Our explanations are based on established sleep science: the structure of sleep cycles, sleep inertia, circadian rhythm research, and public-health sleep duration recommendations.1234 Where the science has uncertainty — and it often does — we say so rather than overstate precision. The calculators use well-known averages (a ~90-minute cycle, ~14 minutes to fall asleep), and we label them as estimates, not personal medical guidance. Each tool page ends with a numbered source list you can open and check.
Our experience promise
The tools work instantly, work on any device, and work without JavaScript for their reference tables. We do not require accounts, and we keep the pages fast and readable. Anonymous visit counts are measured with Google Analytics, and the site may show Google AdSense ads; details are in our Privacy Policy.
Corrections and feedback
Found an error in our science or a bug in a calculator? We genuinely want to know. Write to us at [email protected] with the page URL and the detail that needs fixing.
Sources
Numbers in the text point here. These are peer-reviewed papers, consensus statements, or official public-health pages you can open and check. The calculators still use planning averages; they are not a personal sleep study.
- Patel AK, Reddy V, Shumway KR, Araujo JF. Physiology, Sleep Stages. StatPearls. NCBI Bookshelf. Updated 2024.
- Watson NF, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843–844.
- Hirshkowitz M, et al. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40–43.
- Hilditch CJ, McHill AW. Sleep inertia: current insights. Nature and Science of Sleep. 2019;11:155–165.